Which Planet Has The Longest Day? - Universe Today Universe Today Which Planet Has The Longest Day? Article Updated: 19 Aug , 2016 by Jerry Coffey Just to be clear, this answer to ‘which planet has the longest day’ is based on this criteria: a planets day is how long it takes it to complete one rotation on its axis. This is also referred to as its rotational period. So, Venus has the longest day of any planet in our solar system. It completes one rotation every 243 Earth days. Its day lasts longer than its orbit. It orbits the Sun every 224.65 Earth days, so a day is nearly 20 Earth days longer than its year. Length Of A Day On The Planets In Our Solar System Mercury: 58 days and 15 hours Venus: 243 days Mars: 24 hours, 39 minutes and 35 seconds Jupiter: 9.9 hours Saturn: 10 hours 45 minutes 45 seconds, but can only be approximated because of atmospheric density.

Uranus: 17 hours, 14 minutes and 24 seconds Neptune: 16 hours, 6 minutes and 36 seconds, but it is a bit more complicated than that. The equator and poles rotate at different speeds. You would have to do more research on the planet to fully understand the varying day on Neptune. Now, back to why the Venusian day is longer than its year. Venus is closer to the Sun; therefore, its orbit takes a shorter period of time than its rotation upon its axis. The planet also rotates in retrograde. That means it spins in the opposite direction of the Earth. If you were standing on Venus, you could see the Sun rise in the West and set in the East. A manned Venus flyby mission was proposed in the late 1960s. The mission was planned to launch in late October or early November 1973, and would have used a Saturn V rocket to send three men. The flight would have lasted approximately one year. The spacecraft would have passed approximately 5,000 km from the surface about four months into the flight.

There have been several unmanned probes and flybys of the planet, including MESSENGER and the Venus Express. Future proposed missions include the BepiColombo, Venus InSitu Explorer, and the Venera-D. If you’d like more information on Venus, check out Hubblesite’s News Releases about Venus , and here’s a link to NASA’s Solar System Exploration Guide on Venus . We’ve also recorded an entire episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus . How Long Is A Day On The Other Planets Of The Solar System? - Universe Today Universe Today How Long Is A Day On The Other Planets Of The Solar System? Article Updated: 24 Jan , 2016 by Matt Williams Here on Earth, we tend to take time for granted, never suspected that the increments with which we measure it are actually quite relative. The ways in which we measure our days and years, for example, are actually the result of our planet’s distance from the Sun, the time it takes to orbit, and the time it takes to rotate on its axis. The same is true for the other planets in our Solar System.

While we Earthlings count on a day being about 24 hours from sunup to sunup, the length of a single day on another planet is quite different. In some cases, they are very short, while in others, they can last longer than years – sometimes considerably! Let’s go over how time works on other planets and see just how long their days can be, shall we? A Day On Mercury: Mercury is the closest planet to our Sun, ranging from 46,001,200 km at perihelion (closest to the Sun) to 69,816,900 km at aphelion (farthest). Since it takes 58.646 Earth days for Mercury to rotate once on its axis – aka. its sidereal rotation period – this means that it takes just over 58 Earth days for Mercury to experience a single day. However, this is not to say that Mercury experiences two sunrises in just over 58 days. Due to its proximity to the Sun and rapid speed with which it circles it, it takes the equivalent of 175.97 Earth days for the Sun to reappear in the same place in the sky.

Hence, while the planet rotates once every 58 Earth days, it is roughly 176 days from one sunrise to the next on Mercury. Images of Mercury’s northern polar region, provided by MESSENGER. Credit: NASA/JPL What’s more, it only takes Mercury 87.969 Earth days to complete a single orbit of the Sun (aka. its orbital period). This means a year on Mercury is the equivalent of about 88 Earth days, which in turn means that a single Mercurian (or Hermian) year lasts just half as long as a Mercurian day. What’s more, Mercury’s northern polar regions are constantly in the shade. This is due to it’s axis being tilted at a mere 0.034° (compared to Earth’s 23.4°), which means that it does not experience extreme seasonal variations where days and nights can last for months depending on the season. On the poles of Mercury, it is always dark and shady. So you could say the poles are in a constant state of twilight.

A Day On Venus: Also known as “Earth’s Twin”, Venus is the second closest planet to our Sun – ranging from 107,477,000 km at perihelion to 108,939,000 km at aphelion. Unfortunately, Venus is also the slowest moving planet, a fact which is made evident by looking at its poles. Whereas every other planet in the Solar System has experienced flattening at their poles due to the speed of their spin, Venus has experienced no such flattening. Venus has a rotational velocity of just 6.5 km/h (4.0 mph) – compared to Earth’s rational velocity of 1,670 km/h (1,040 mph) – which leads to a sidereal rotation period of 243.025 days. Technically, it is -243.025 days, since Venus’ rotation is retrograde. This means that Venus. rotates in the direction opposite to its orbital path around the Sun. The planet Venus, as imagined by the Magellan 10 mission.

Credit: NASA/JPL So if you were above Venus’ north pole and watched it circle around the Sun, you would see it is moving clockwise, whereas its rotation is counter-clockwise. Nevertheless, this still means that Venus takes over 243 Earth days to rotate once on its axis, which means that many, many days pass between one sunrise and the next. This may seem odd, until you consider that a single Venusian (or Cytherean) year works out to 224.701 Earth days. Yes, Venus takes a little more than 224 days to complete a single orbital period, but over 243 days to experience a single day and night cycle. So basically, a single Venusian day is longer than a Venusian year! Good thing Venus has other things in common With Earth, because it is sure isn’t its diurnal cycle! A Day On Earth: When we think of a day on Earth, we tend to think of it as a simple 24 hour interval. In truth, it takes the Earth exactly 23 hours 56 minutes and 4.1 seconds to rotate once on its axis.

Meanwhile, on average, a solar day on Earth is 24 hours long, which means it takes that amount of time for the Sun to appear in the same place in the sky. Between these two values, we say a single day and night cycle lasts an even 24. At the same time, there are variations in the length of a single day on the planet based on seasonal cycles. Due to Earth’s axial tilt, the amount of sunlight experienced in certain hemispheres will vary. The most extreme case of this occurs at the poles, where day and night can last for days or months depending on the season. At the North and South Poles during the winter, a single night can last up to six months, which is known as a “polar night”. During the summer, the poles will experience what is called a “midnight sun”, where a day lasts a full 24 hours. So really, days are not as simple as we like to imagine. But compared to the other planets in the Solar System, time management is still easier here on Earth. A Day On Mars: In many respects, Mars can also be called “Earth’s Twin”.

In addition to having polar ice caps, seasonal variations , and water (albeit frozen) on its surface, a day on Mars is pretty close to what a day on Earth is. Essentially, Mars takes 24 hours 37 minutes and 22 seconds to complete a single rotation on its axis. This means that a day on Mars is equivalent to 1.025957 days. The seasonal cycles on Mars, which are due to it having an axial tilt similar to Earth’s (25.19° compared to Earth’s 23.4°), are more similar to those we experience on Earth than on any other planet. As a result, Martian days experience similar variations, with the Sun rising sooner and setting later in the summer and then experiencing the reverse in the winter. However, seasonal variations last twice as long on Mars, thanks to Mars’ being at a greater distance from the Sun. This leads to the Martian year being about two Earth years long – 686.971 Earth days to be exact, which works out to 668.5991 Martian days (or Sols).

As a result, longer days and longer nights can be expected last much longer on the Red Planet. Something for future colonists to consider! Sunrise at Gale Crater on Mars. Gale is at center top with the mound in the middle, called Mt. Sharp (Aeolis Mons.) A Day On Jupiter: Given the fact that it is the largest planet in the Solar System, one would expect that a day on Jupiter would last a long time. But as it turns out, a Jovian day is officially only 9 hours, 55 minutes and 30 seconds long, which means a single day is less than a third the length of an Earth day. This is due to the gas giant having a very rapid rotational speed, which is 12.6 km/s (45,300 km/h, or 28148.115 mph) at the equator. This rapid rotational speed is also one of the reasons the planet has such violent storms. Note the use of the word officially. Since Jupiter is not a solid body, its upper atmosphere undergoes a different rate of rotation compared to its equator.

Basically, the rotation of Jupiter’s polar atmosphere is about 5 minutes longer than that of the equatorial atmosphere. Because of this, astronomers use three systems as frames of reference. System I applies from the latitudes 10° N to 10° S, where its rotational period is the planet’s shortest, at 9 hours, 50 minutes, and 30 seconds. System II applies at all latitudes north and south of these; its period is 9 hours, 55 minutes, and 40.6 seconds. System III corresponds to the rotation of the planet’s magnetosphere, and it’s period is used by the IAU and IAG to define Jupiter’s official rotation (i.e. 9 hours 44 minutes and 30 seconds) Jupiter and Io capturing the Sun. Image Credit: NASA/JPL So if you could, theoretically, stand on the cloud tops of Jupiter (or possibly on a floating platform in geosynchronous orbit), you would witness the sun rising an setting in the space of less than 10 hours from any latitude. And in the space of a single Jovian year, the sun would rise and set a total of about 10,476 times.

A Day On Saturn: Saturn’s situation is very similar to that of Jupiter’s. Despite its massive size, the planet has an estimated rotational velocity of 9.87 km/s (35,500 km/h, or 22058.677 mph). As such Saturn takes about 10 hours and 33 minutes to complete a single sidereal rotation, making a single day on Saturn less than half of what it is here on Earth. Here too, this rapid movement of the atmosphere leads to some super storms , not to mention the hexagonal pattern around the planet’s north pole and a vortex storm around its south pole. And, also like Jupiter, Saturn takes its time orbiting the Sun. With an orbital period that is the equivalent of 10,759.22 Earth days (or 29.4571 Earth years), a single Saturnian (or Cronian) year lasts roughly 24,491 Saturnian days. However, like Jupiter, Saturn’s atmosphere rotates at different speed depending on latitude, which requires that astronomers use three systems with different frames of reference.

System I encompasses the Equatorial Zone, the South Equatorial Belt and the North Equatorial Belt, and has a period of 10 hours and 14 minutes. System II covers all other Saturnian latitudes, excluding the north and south poles, and have been assigned a rotation period of 10 hr 38 min 25.4 sec. System III uses radio emissions to measure Saturn’s internal rotation rate, which yielded a rotation period of 10 hr 39 min 22.4 sec. This portrait looking down on Saturn and its rings was created from images obtained by NASA’s Cassini spacecraft on Oct. 10, 2013. Credit: NASA/JPL-Caltech/Space Science Institute/G. Ugarkovic Using these various systems, scientists have obtained different data from Saturn over the years. For instance, data obtained during the 1980’s by the Voyager 1 and 2 missions indicated that a day on Saturn was 10 hours 39 minutes and 24 seconds long.

In 2004, data provided by the Cassini-Huygens space probe measured the planet’s gravitational field, which yielded an estimate of 10 hours, 45 minutes, and 45 seconds (± 36 sec). In 2007, this was revised by researches at the Department of Earth, Planetary, and Space Sciences, UCLA, which resulted in the current estimate of 10 hours and 33 minutes. Much like with Jupiter, the problem of obtaining accurate measurements arises from the fact that, as a gas giant, parts of Saturn rotate faster than others. A Day On Uranus: When we come to Uranus, the question of how long a day is becomes a bit complicated. One the one hand, the planet has a sidereal rotation period of 17 hours 14 minutes and 24 seconds, which is the equivalent of 0.71833 Earth days. So you could say a day on Uranus lasts almost as long as a day on Earth. It would be true, were it not for the extreme axial tilt this gas/ice giant has going on.

With an axial tilt of 97.77°, Uranus essentially orbits the Sun on its side. This means that either its north or south pole is pointed almost directly at the Sun at different times in its orbital period. When one pole is going through “summer” on Uranus, it will experience 42 years of continuous sunlight. When that same pole is pointed away from the Sun (i.e. a Uranian “winter”), it will experience 42 years of continuous darkness. Uranus as seen by NASA’s Voyager 2. Credit: NASA/JPL Hence, you might say that a single day – from one sunrise to the next – lasts a full 84 years on Uranus! In other words, a single Uranian day is the same amount of time as a single Uranian year (84.0205 Earth years). In addition, as with the other gas/ice giants, Uranus rotates faster at certain latitudes. Ergo, while the planet’s rotation is 17 hours and 14.5 minutes at the equator, at about 60° south, visible features of the atmosphere move much faster, making a full rotation in as little as 14 hours.

A Day On Neptune: Last, but not least, we have Neptune. Here too, measuring a single day is somewhat complicated. For instance, Neptune’s sidereal rotation period is roughly 16 hours, 6 minutes and 36 seconds (the equivalent of 0.6713 Earth days). But due to it being a gas/ice giant, the poles of the planet rotate faster than the equator. Whereas the planet’s magnetic field has a rotational speed of 16.1 hours, the wide equatorial zone rotates with a period of about 18 hour. Meanwhile, the polar regions rotate the fastest, at a period of 12 hours. This differential rotation is the most pronounced of any planet in the Solar System, and it results in strong latitudinal wind shear. Reconstruction of Voyager 2 images showing the Great Black spot (top left), Scooter (middle), and the Small Black Spot (lower right). Credit: NASA/JPL In addition, the planet’s axial tilt of 28.32° results in seasonal variations that are similar to those on Earth and Mars. The long orbital period of Neptune means that the seasons last for forty Earth years.

But because its axial tilt is comparable to Earth’s, the variation in the length of its day over the course of its long year is not any more extreme. As you can see from this little rundown of the different planets in our Solar System, what constitutes a day depends entirely on your frame of reference. In addition to it varying depending on the planet in question, you also have to take into account seasonal cycles and where on the planet the measurements are being taken from. As Einstein summarized, time is relative to the observer. Based on your inertial reference frame, its passage will differ. And when you are standing on a planet other than Earth, your concept of day and night, which is set to Earth time (and a specific time zone) is likely to get pretty confused! We have written many interesting articles about how time is measured on other planets here at Universe Today. For example, here’s How Long Is A Year On The Other Planets? , Which Planet Has the Longest Day? , The Rotation of Venus , How Long Is A Day on Mars? and How Long Is A Day On Jupiter? .

If you are looking for more information, check out Our Solar System at Space.com Astronomy Cast has episodes on all the planets, including Episode 49: Mercury , and Episode 95: Humans to Mars, Part 2 – Colonists Share this: “Since it takes 58.646 Earth days for Mercury to rotate once on its axis – aka. its sidereal rotation period – this means that it takes just over 58 Earth days for Mercury to experience a single sunrise and sunset.” Sorry, Matt, but this is precisely incorrect, and I stopped reading at this point. 1) Sideral = stars; solar = Sol/The Sun. Mercury’s sidereal day/rotation period is indeed 58.646 Earth days. This means that it takes 58.646 Earth days for background stars (NOT the Sun) to rise, set, and then rise again. 2) “Days” are measured from sunrise to sunrise, not sunrise to sunset as you’ve indicated; if you think about the 24hrs of a Terran solar day you will see instantly that this is true.

3) Mercury’s solar day is heavily influenced by the Mercury’s speedy orbit around the sun; while Mercury rotates, it also revolves, leading to a Nabooan solar day of ~176 Earth days. This same effect of rotation + revolution is why sidereal and solar days are different in the first place — Earth’s solar day is ~24hrs, while its sidereal day is ~4min shorter — and is why the stars visible in our night sky locally change from season to season. 4) Finally, the effect of revolution + Mercury’s noticeably elliptical orbit + rotation leads to some bizarre timing when it comes local sunrise, sunset, noon, and midnight in various places on the planet as well. In some places, one ends up with Sol crossing overhead three separate times between local sunrise & sunset; in others “Sunrise” is spread out over weeks (Earth reckoning) as Sol rises above the horizon, then sets completely, then rises again to cross the sky, only to perform the same dance in reverse upon “Sunset” (set, rise again, set again). Thought we maybe discussed this once before, somewhere…. What planet has the longest day? | Reference.com What planet has the longest day?

A: Quick Answer Venus has the longest day of any major planet in the solar system, taking 243 days to complete a full rotation along its axis. Due to its slow rotation, Venus has a day that is longer than its year. Full Answer Venus rotates in the opposite direction of the other planets. Due to its unique rotational direction, the time between sunrises on Venus is just under 117 Earth days. Theory regarding the rotational direction of the planet suggests that Venus once spun in the same direction as the other planets, but some event, such as extremely strong atmospheric tides due to the sun's gravitational pull, occurred in the past that caused it to flip its axis 180 degrees. How long is one day on other planets? :: NASA Space Place How long is one day on other planets? Share: Tweet How long are days on other planets? One day is the time it takes a planet to spin around and make one full rotation. Here on Earth that takes 24 hours. How long are days on other planets in our solar system? And what is the best way to show the answer to this question? Let’s look at a few options.

Option 1: A Paragraph We can write a paragraph about how long days last on other planets. On Mercury a day lasts 1,408 hours, and on Venus it lasts 5,832 hours. On Earth and Mars it’s very similar. Earth takes 24 hours to complete one spin, and Mars takes 25 hours. The gas giants rotate really fast. Jupiter takes just 10 hours to complete one rotation. Saturn takes 11 hours, Uranus takes 17 hours, and Neptune takes 16 hours. Reading that paragraph took a while, and it’s hard to find all the numbers. Let’s see how it looks if we put it in a table. Option 2: A Table Neptune 16 hours That’s a little bit better. We can look up and down at the numbers and can compare them more easily. But wouldn’t it be nice if we could see how big those differences are? Let’s make a graph with these numbers! Option 3: A Graph To start, make a number line that starts at 0 and goes to the highest number you need to include.

This first graph will only have Earth, Mars, Jupiter, Saturn, Uranus, and Neptune on it. We’ll save Mercury and Venus for later. You'll see why in a minute. The longest day among those planets is 25 hours. That means our number line will go up to 25. Label the number line so you remember it represents hours. And write what information the graph will have at the top. Along the bottom, write the names of the planets. Make a dot above the name of the planet next to the number of hours its day takes. Our graph is coming together! What do we do now? Color in the area below the dot to make a bar graph. Now we can easily see which planet has the longest day, the shortest day, and everything in between. This is much easier that reading a list of numbers, don’t you think? < PREVIOUS NEXT > But what do we do about Mercury and Venus? Their days are thousands of hours long. How do we make a graph for those?

We make a number line, but instead of numbers 1, 2, 3… we will use 1,000, 2,000, 3,000… Make a number line that goes all the way up to 6,000. Along the bottom, write Mercury and Venus. Above Mercury, mark a dot a little less than halfway between 1,000 and 2,000. It’s not going to be perfect, but that’s okay. Now make a dot a little under 6,000 for Venus. Do you think we can include Earth, Mars, Jupiter, Saturn, Uranus, and Neptune on here? Their dots would be so close to 0 it would be hard to tell the difference between them. Graphs work best when the numbers are similar in size, usually with the same number of digits. < PREVIOUS NEXT > Now that you know how to make a graph, you can show all kinds of information this way. You can graph the time it takes to get to school each day, the number of pieces of pizza your friends can eat, and how many people like the color blue or green. Go on and get graphing!

article last updated December 1, 2016 The Solar System: Mercury | The Institute for Creation Research The Solar System: Mercury Resources › Physical Sciences Resources › Astronomy The smallest planet of our solar system holds some big mysteries for secular astronomers, and it continues to delight creationists. Mercury is only 38 percent the diameter of Earth, making it the smallest and least massive of the eight planets. It is the innermost planet of the solar system, orbiting the sun at a distance of only 36 million miles. That is nearly three times closer to the sun than Earth is. Mercury is a solid, rocky world, with only a trace of an atmosphere. It has mountains, valleys, plains, and craters—lots and lots of craters! In appearance, Mercury resembles a 40 percent larger (in radius) version of the moon. But when it comes to creation research of the early solar system, Mercury provides many interesting clues. The unusual characteristics of this world make for an intriguing study. A World of Extremes Since it is closest to the sun, Mercury has the shortest “year” of any planet, taking only 88 Earth days to complete one orbit.

So every time Earth completes one orbit, Mercury has already made four trips around the sun. On the other hand, it has the longest solar day of any planet. A hypothetical observer on Mercury’s surface would only see a sunrise every 176 Earth days! The “sidereal” (relative to the stars) rotation rate of Mercury is 59 Earth days. If we could somehow watch Mercury through a telescope from a distant star, we would see it rotate one time every 59 days. This is called a “sidereal day” because sidereal means “star,” and we are watching from the stars in this scenario. On the other hand, if we could somehow watch Mercury from the position of the sun, Mercury would appear to turn once every 176 days. This is called a “solar day.” The reason for the difference is that Mercury orbits the sun as it rotates.1 This is also true of the other planets, though the difference is generally much less.2 Mercury’s slow rotation results in some other interesting effects. A given spot on Mercury is in direct sunlight for about 88 continuous Earth days at a time.

And since Mercury is three times closer to the sun than Earth is, and since there is no substantial atmosphere to transport the heat, the surface temperature on the day side of Mercury can reach 800 degrees Fahrenheit—more than hot enough to melt lead. Perhaps even more surprising is that the temperature on the night side of Mercury can drop to -280 degrees Fahrenheit! This is because it is in continual darkness for up to 88 days and there is no significant atmosphere to prevent the nighttime surface from radiating virtually all its heat into space. These extremes lead to some interesting hypothetical scenarios. Suppose your spaceship ran out of fuel, but not before you were able to land near the equator of Mercury. Thankfully, you have landed on the night side (barely), and your spacesuit protects you from the bitter cold surface. But it won’t protect you from the 800-degree daytime temperatures that are about to occur when the sun rises in just a couple of hours! Thanks to Mercury’s very long day, you could begin jogging west at a leisurely pace of two miles per hour.

As long as you can maintain that pace, you could stay ahead of the sunrise and remain safely in the night for as long as it takes for the rescue ship to arrive. Effectively, you would be jogging in the opposite direction that the planet rotates, and at about the same rate, thereby permanently remaining in the safe shadow of night. Mercury’s Strange Orbit Another curious aspect of Mercury’s rotational (sidereal) period is that it is precisely two thirds of its orbital period. So Mercury turns on its axis three times every time it orbits the sun twice. In astronomy, whenever the ratio of two periods can be expressed by a simple fraction, it is called a “resonance.” Mercury is the only planet in our solar system whose rotation period and orbital period are in resonance. There is a reason for this, and it involves Mercury’s orbit. Mercury has the most eccentric orbit of any planet—meaning that its orbit is noticeably elliptical and not as circular as the other planets. From Kepler’s Second Law (see “ The Solar System” article),3 a planet in an elliptical orbit moves faster when closer to the sun than it does when farther away.

The point of closest approach is called perihelion, and this is when Mercury moves the fastest. The most distant point is aphelion, and this is where it orbits the slowest. But Mercury’s rotation rate does not change. Interestingly, when Mercury is near perihelion, its rotation rate essentially matches its revolution rate, such that it keeps the same side pointed at the sun for several weeks.4 This configuration is very gravitationally stable.5 It would be strange to watch this phenomenon from the surface of Mercury itself—if we could somehow survive there. Imagine we begin by watching a very slow sunrise. It takes almost 20 hours between the first moment when the top of the sun peeks over the horizon and the time when the entire sun is visible. The sun seems enormous from Mercury’s perspective—appearing two and a half times larger in the sky than it does on Earth and over six times brighter! The sky remains black even when the sun is up, since Mercury lacks the comfort of Earth’s thick atmosphere. The sun then gradually climbs higher in the sky over the next several weeks. The stars also rise in the east, seeming to move at about twice the speed of the sun.

But as Mercury approaches perihelion, the sun seems to gradually slow its upward path, while the stars continue to rise and set at their usual pace. The sun is now noticeably larger than we witnessed at sunrise and over three times larger than it appears from Earth—and ten times brighter! Then the sun gradually comes to a complete stop and begins to travel slowly backward just slightly for about a week. We might feel like Hezekiah ( Isaiah 38:8 )!6 It then slows to a stop once again and reverses direction once more. The sun then gradually resumes its forward path, shrinking and fading a bit as Mercury moves toward aphelion. The sun eventually sets in the west, roughly three months after sunrise. Observing Mercury Since it is so close to the sun, Mercury appears quite bright in our nighttime sky, rivaling the brightest stars. Yet most people have never seen it. The planet can be a challenge to locate because it orbits so close to the sun and is easily lost in the glare. Most other planets can be seen late at night, when the sky is quite dark.

But not Mercury—it is only visible at twilight and only at certain times of the year when it is in a part of its orbit that appears (in angle) most distant from the sun. This position is called “greatest elongation.” At such times, it is possible to see Mercury just after sunset for “eastern elongations” or just before sunrise for “western elongations.”7 Thanks to Mercury’s short period, greatest elongations happen six (sometimes seven) times a year. Our next chance to see Mercury will be on October 9, 2013, or a few days before or after this. Go outside 20 to 30 minutes or so after sunset and look low to the west, just above the horizon. Venus will also be visible and bright and much higher in the sky. Look between Venus and the point where the sun sets and you will see the much-fainter Mercury. Mercury Confirms Creation Since Mercury is so close to the sun, and only visible low in the sky after sunset or before sunrise, Earth-based telescopic views of Mercury tend to be rather unimpressive and unrevealing.

That all changed when NASA sent the Mariner 10 spacecraft to visit Mercury in 1974. During several flyby encounters, Mariner 10 was able to image much of the day side of Mercury in unprecedented detail. It also measured a substantial magnetic field for this tiny planet. This is disturbing news for secularists who believe that our solar system is billions of years old, because a small planet like Mercury should not be able to maintain a magnetic field for so long. But this doesn’t surprise creationists. Physicist D. Russell Humphreys, Ph.D., has an interesting biblically based model that is able to account for the current strength of planetary magnetic fields based on their true age of about 6,000 years.8 His model lines up quite well with the current measured field strengths of the planets. Dr. Humphreys had also predicted that Mercury’s magnetic field will show measurable decay since the 1974 measurements. And this was confirmed by the more recent (2008-2013) Messenger spacecraft.9 Mercury has also been used to confirm other aspects of science.

Theoretical physicist Albert Einstein’s general theory of relativity indicates that gravitational fields affect the measurement of space and time. One such prediction of relativity is that Mercury’s perihelion should “precess” at a different rate than classical physics would predict. “Precess” means that the ellipse of Mercury’s orbit slowly rotates such that the angular location of the perihelion (and aphelion) gradually changes.10 Observations have confirmed Einstein’s prediction, bolstering our confidence in general relativity. Creationists have long debated when and how the craters we find in our solar system actually happened. Were the planets created with craters? Did God use some process to make the planets on Day Four such that the craters are the last material He brought to impact the surface? Did they happen after the Curse or during the Flood year? And if so, why? Mercury may also hold the key to theories of cratering. Most other rocky worlds in our solar system have tectonic, atmospheric, and volcanic activity that can remove evidence of any previous craters. But not Mercury. Its pristine surface may be a window into the original conditions of our solar system.11 What other secrets can we discern from this fascinating little world?

Time will tell. References To make this easier to understand, suppose that Mercury’s rotation and revolution periods were both exactly the same: 88 days. In this case, a person watching from a distant star would see Mercury rotate once in 88 days. But the sun would never see the other side of Mercury because the planet would keep its same “face” pointed toward the sun as it revolves around the sun. Likewise, a person standing on Mercury’s surface would never see a sunrise or sunset, if this were the case. The sidereal day would be 88 days, and the solar day would essentially be infinity. Since other planets also orbit the sun, their solar days are also different than their sidereal day. But the difference tends to be much smaller than with Mercury. Earth has only a four-minute difference between its solar and sidereal days. The reason Mercury exhibits such an enormous difference is because the length of its sidereal day is comparable to the length of its year. Lisle, J. P. 2013. The Solar System . Acts & Facts. 42 (6): 10-12.

At the time of perihelion, the orbital angular speed actually slightly exceeds the rotation angular speed for about one week. An observer on the surface would see the sun apparently move slightly backward in the sky for that one week. Some orbital resonances are stable and self-correcting, such as Mercury’s. Others are unstable, such that an orbiting body will be continually perturbed until it is ejected into a different orbit altogether. This appears to be the reason why there is a deficit of asteroids having simple resonances with Jupiter’s orbit. These resonance orbits are known as the Kirkwood gaps. Critics sometimes declare that God cannot do certain things, such as make the sun go backward as He did for Hezekiah. Such things are simply not possible, we are told. Yet this happens every three months on Mercury. It is probably not the same mechanism that God used for Hezekiah. Nonetheless, it is to the shame of those critics who attempt to tell God what He cannot do. “Eastern” denotes that Mercury is east of the sun. It therefore can be seen in our western sky just after sunset. Conversely, “western” elongations are those in which Mercury is farthest separated to the west of the sun.

At such a time, Mercury can be viewed in the eastern sky just before sunrise. Thomas, B. Mercury’s Fading Magnetic Field Fits Creation Model . Creation Science Update. Posted on icr.org October 30, 2011, accessed June 1, 2013. The perihelion distance does not change, only its angle. Imagine Mercury’s orbit lined up with a clock such that the perihelion is aligned with 12:00 and the aphelion is aligned with 6:00. As Mercury orbits the sun, the ellipse of its orbit slowly rotates counterclockwise such that at a later time perihelion would point to 11:30 and aphelion would point to 5:30. The precession of Mercury’s orbit is very slow, amounting to only 575 arc-seconds per century. Of this rate, 532 arc-seconds per century are due to gravitational perturbations of the other planets. The remaining 43 arc-seconds per century are due to the effects of general relativity. The agreement between the theoretical predictions and the observations is remarkable. 11.

This may also be true of the moon. Yet some creationists believe that the moon was impacted more recently by comets or a meteor stream in association with the Flood of Genesis 6 -8. It is unlikely that Mercury would have been strongly affected by the Flood due to its great distance. So differences between Mercury and the moon may help us understand better when these events occurred. * Dr. Lisle is Director of Physical Sciences at the Institute for Creation Research and received his Ph.D. in Astrophysics from the University of Colorado. Cite this article: Lisle, J. 2013. The Solar System: Mercury. Acts & Facts. 42 (8): 10-12.

Question: Which planet has the longest day?
Answer: Venus